Defective membrane repair results in disease, as do also genetic defects that render cells more susceptible to disruption injury. In both cases, pathology might be eliminated if repair failure could be reduced, preventing rapid cell death via necrosis. We have begun a search for non-toxic compounds that can enhance cell membrane repair and have discovered a promising candidate. Preliminary results reveal that vitamin E potently enhances defective plasma membrane repair in both HeLa and C2C12 cells. We will confirm and further characterize this result, determining optimal dosing conditions and testing additional cell types. How does vitamin E promote membrane repair? One possibility is as an antioxidant. We hypothesize that the antioxidant property of vitamin E is crucial in promoting repair. Preliminary evidence supports this hypothesis and we will test two important predictions: that antioxidants other than vitamin E will also promote membrane repair, and that additional oxidant challenge will inhibit. Severe deficiency in vitamin E results in lethal muscular dystrophy in animal models and mild deficiency is associated with muscle-related problems in humans. Conversely, vitamin E supplementation, in mice and in humans, protects muscle from injury by eccentric contractions, which induce high levels of myocyte membrane disruption. Thus, skeletal muscle is a logical starting point for in vivo tests of the biological role of antioxidants in membrane repair. We hypothesize that vitamin E at physiological concentrations in myocytes is required for skeletal muscle membrane repair. We will test two key predictions of this hypothesis: that, in normal mice, vitamin E dietary deficiency will result in defective skeletal muscle myocyte repair and that, conversely, vitamin E or other antioxidant supplementation will enhance repair by myocytes defective in this ability (derived from dystrophic mouse models). This application has both biological and translational significance. It presents and will rigorously test using advanced microscope techniques a new paradigm for understanding the physiological role of vitamin E: namely, that is required for membrane repair in skeletal muscle. And it identifies the first non-toxic class of agents that can enhance cell membrane repair-antioxidants such as vitamin E-and will test the ability of these compounds to restore repair in cell models of muscular dystrophy.